Descriptions

Tobiano is a dominant pattern of white spotting that occurs in certain breeds of horses. This pattern is often desirable and some breeders will purchase a genetic test to help distinguish homozygous from heterozygous horses for breeding purposes. Some tobiano horses have smaller dark spots on the white patches of their coat, known as "ink spots" or "paw prints" which are commonly believed by breeders to be associated with homozygosity. Sixty-six tobiano Paint horses were surveyed to assess their genotype (homozygous or heterozygous for tobiano) and their phenotype (presence or absence of ink spots). Thirty-one of the horses with ink spots were then classified as having fewer than five, or five or more ink spots. The results indicate that ink spots do not occur at random (p < .001) and the presence of five or more ink spots is associated with homozygosity (p <.001).